Wireless performance between different VLANs

[tiago.molinos]

Hi,

I have a problem regarding throughput over wireless when the peers of the data transfer are in different VLAN (separate networks).

Topology:

I have a 3560 L3 switch configured with two VLANs, VLAN1 is the PC Wired network and VLAN2 is the PC Wireless network.

Connected to this switch I have a 1602i standalone access-point.

I have connected two PCs via Gigabit Ethernet ports to both VLANs (wireless is disabled).

I have one wireless client connected via 802.11an (disabled 802.11bgn to rule out interferences) using 40MHz channel width in the wireless network (VLAN2)

Device description:

PC1 - Connected via Gb ethernet to VLAN1;

PC2 - Connected via Gb ethernet to VLAN2;

PC3 - Connected via Gb ethernet to VLAN1;

WPC1 - Connected via 802.11n to VLAN2;

Here's the the tests I've made:

I've used both iperf and multiple paralel FTP sessions with similar results.

PC1 -> PC3

447 Mbits/sec

Note: no routing involved, no wireless involved

PC1 -> PC2

220 Mbits/sec

Note: inter-vlan routing involved, no wireless involved

PC2 -> WPC1

80 Mbits/sec

Note: no routing involved

PC1 -> WPC1

9.8 Mbits/sec <== PROBLEM

Note: inter-vlan routing involved

As you can see I have nearly a 10x factor decrease in performace in the last test presented. I can't find why this happens!

I've already updated both the access-point and the switch to the latest version avaliable.

I've also used an old AP1100G and got the same result, around 9.8Mbits/sec when in different networks and around 17Mbit/sec when in the same network.

I've tested with diffent security settings in the wireless ssid, but I always get the same results... a huge performance degradation when connecting two devices in different VLANs.

Any suggestion? Thanks!

[tiago.molinos]

We’ve found the origin of the problem. It had to do with a badly configured gateway IP address in the DHCP Pool, for the network in VLAN1. We were experiencing asymmetric routing with one leg of the communication been routed through a Cisco 800 series. We've found that this issue was ongoing for the past few months.

Testing a new access-point took us to wrongly think this was a wireless issue.

Thank you for your help. You have been really useful!

[Rasika Nayanajith]

Glad you finally identified the issue.

[Scott Fella]

Yeah good job!!!!

Thanks,

Scott

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